Sea Level Rise Seminar, 2023-03-14
Speaker: Nicole Schlegel (JPL, Caltech)
Title: Attributing pieces of the pie: detangling uncertainty in ice-sheet model projections
Abstract: Numerical ice sheet models are invaluable tools for bounding Antarctica's response to ocean and atmospheric change. However, model-based continental-scale projections of Antarctica’s grounding line evolution remain largely uncertain, as estimates of sea-level contribution can vary by up to an order of magnitude. This is partly due to the fact that model projections strongly depend on the model's boundary conditions and climate forcing. Here, we aim to improve the understanding of how variations in model forcing and boundary conditions affect ice sheet model simulations. In this talk, I discuss how we do so, by taking advantage of JPL's Ice-sheet and Sea-level System Model (ISSM) and various uncertainty quantification methods available through the ISSM framework, to detangle and compare sources of model uncertainty in century-scale simulations of the Antarctic Ice Sheet evolution. Our experiments suggest that Antarctica’s most dynamic glaciers exhibit threshold responses to increased ocean melt, and the thresholds for regional collapse appear to be strongly dependent on the characteristics of bathymetric features inland of the current grounding line. I discuss ongoing efforts to identify the most influential bedrock features and to quantify how bedrock error propagates as uncertainty in simulated Antarctic sea-level projections. This includes an overview of our efforts to use model experiments to constrain the resolution of bedrock topography needed to more accurately predict the probability of key glaciers exceeding their thresholds for collapse in the near future.
